integration of stormwater master plans with watershed plans the link between flooding and...
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Integration Of Stormwater Master Plans with Watershed Plans
The Link between Flooding and Development
September 23, 2008
Bob Murdock, P.E., CFM
The Nexus of Watershed Planning with Stormwater Management
The interconnection of flood management actions within broader water resources management and land use planning;
The value of coordinating across geographic and agency boundaries The need to evaluate opportunities and potential impacts from a system
perspective The importance of environmental stewardship and sustainability.
Why consider the watershed within our stormwater planning?
Specific Benefits:
Floods Water Quality Environment - Quality of Life
Why consider the watershed within our stormwater planning?
Central Message:
What you do in one part of the watershed affects the rest…..stormwater management and development
1 2 3 4 5 6
1990s
1980s
1970s
1960s
1950s
1940s
1930s
1920s
1910s
BILLIONS (adjusted to 1999 dollars)
Trends in Flood Damages
$6 billion annually
Four-fold increase from early 1900s
Per Capita Damages increased by more than a factor of 2.5 in the previous century in real dollar terms
$$2.2
$$2.0
$$2.9
$$2.4
$$3.4
$$2.2
$$4.9
$$3.3
$$5.6
Demographic Trends: The Future
As We Move Into the Next Generation Things Will Be Much More Challenging For Floodplain and Stormwater Managers
Dr. Arthur “Chris” Nelson, FAICP Leadership in a New Era “More than half of the built environment of the United
States we will see in 2025 did not exist in 2000”
Journal of the American Planning Association, Vol. 72, No. 4, Autumn 2006© American Planning Association, Chicago, IL
As printed in www.architectmagazine.com.
USA Today April 29, 2008
Chris Nelson Tells APA Convention That: In the Next One Hundred Years the US
Population Will Grow To:
Any Guesses?
So consider…..
Even if we perfectly implement current standards,damages and flood heights will increase
Remember, we have done a number of positive things, both non-structural and structural, but…We’ll discuss why that is…
Components of Impervious Cover in the Urban Landscape
Roads
ParkingParking
BuildingsBuildings
SidewalksSidewalks
DrivewaysDriveways
Center for Watershed Protection 6
Agriculture Undeveloped
Existing Development
1940sUndeveloped
7Center for Watershed Protection
Agriculture Undeveloped
Existing Development
1950sUndeveloped
8Center for Watershed Protection
Agriculture Undeveloped
Existing Development
1960sUndeveloped
9Center for Watershed Protection
Agriculture
Existing Development
1970sDeveloped
Developed
10Center for Watershed Protection
Existing Development
1990s
UnderConstruction
Developed
Developed
Center for Watershed Protection 11
10% 40%25%
Good
Fair
Poor
Watershed Impervious Cover
Str
eam
Qu
alit
y
60% 100%
Sen
siti
ve
Imp
acte
d
Non-Supporting
Impervious Cover Model
Urban Drainage
10% IC10% IC
30% IC30% IC
18
19
60% IC60% IC
19
IC and Stream Habitat
8-108-10%
2020%
30%30%> 65%> 65%
< 5%< 5%
Questions for your Plan Development
What kind of practices do you want consider and encourage within your master plan and ordinance, given what we know about impervious cover and its effect on watershed health?
1st - Conservation
ExistingCommercial
ExistingLow DensityResidential
Existing Medium Density
Residential Currently Zoned Medium Density ResidentialPropose changing zoning to Residential Cluster Development
58
Photo Copyright 1999, Center for Watershed Protection
Buffer Width
Questions for your Ordinance Development
What kind of practices do you want consider and encourage within your master plan and ordinance, given what we know about impervious cover and its effect on watershed health?
2nd: Site Specific Low Impact Development
Cul-de-SacsCul-de-Sacs
Not so good.
Good.
72
Street WidthStreet Width
Not so good.
Good. 73
Not so good.
Good.
ConventionalSubdivision
Open SpaceSubdivision
Parking lots are often underutilized and can be minimized through better
site design techniques.
Copyright 2000, Center for Watershed Protection
3rd:
For the Engineering Geeks
Central Message Your ordinance actions do affect others in the
watershed
Hydrographs for Pre and Post Development Conditions
Source: California State Water Resources Control Board Stormwater Program And The Water Board Academy, 2007
Q
Post-Development with Conventional Detention
Source: California State Water Resources Control Board Stormwater Program And The Water Board Academy, 2007
Traditional Stormwater Detention Practice
Q
Watershed with Combined Flows at Tributaries
Source: Georgia Stormwater Manual, 2001
Volume Effects at Downstream Tributaries
Source: Georgia Stormwater Manual, 2001
Q Q
Q
Post-development hydrograph response to LID controls
Source: California State Water Resources Control Board Stormwater Program And The Water Board Academy, 2007
Establish Hydromodification Management Plans (HMPs)
HMPs are now a requirement of various regional regulatory programs including:
San Francisco Bay Area (discharge rates and flow durations maintained from 0.1 x Q2yr to Q10yr; erosion potential evaluation)
San Diego County (Permit requires LID measures and HMPs)
New Jersey (requires 100% of pre-construction groundwater recharge, and HMPs for various events)
Portland (incentives for green infrastructure, reduced utility rates for green onsite stormwater management)
Washington DC – Anacostia River (On-site retention of 1-in rainfall and Wtr Qual treatment for 2-yr storm)
Some Closing Points:
No Watershed Study – No Big Deal Reach out to other communities and watershed
organizations EPA and other agencies do offer grants for
watershed studies Remember – A community’s stormwater actions
affects the entire watershed, so ask if the actions will make a difference….
Integration Of Stormwater Master Plans with Watershed Plans
QUESTIONS?
Bob Murdock, P.E., CFM
312-575-3946